BASES AND OBJECTIVE: The ventilatory threshold (VT) has been used as an indicator of the lactate threshold and used as a reference for endurance training. The purpose of this study was to compare the maximal oxygen uptake (VO2MAX) and the VT during a bicycle ergometer test between cyclists and triathletes. METHODS: VO2MAX was determined by open-circuit spirometry in 12 cyclists and 13 triathletes. The ventilatory equivalent for oxygen consumption, the ventilatory equivalent for carbon dioxide production, partial pressure of oxygen and the partial pressure of carbon dioxide (PETCO2) were plotted in function of the workload. The criterion to determinate the VT was when the ventilatories equivalents increased with a concomitant reduction in the PETCO2. RESULTS AND CONCLUSIONS: There was difference (p < 0.05) for the VO2MAX (57.72 ± 3.92 and 49.47 ± 5.96 kg·ml-1·min-1), VO2 at VT (46,91 ± 5,96 and 42,16 ± 4,97 kg·ml-1·min-1), and maximal heart rate (FCMAX) (188.83 ± 12.89 and 174.61 ± 13.79 bpm) between cyclists and triathletes, respectively. Therefore, there was no difference for the %VO2MAX (81.42 ± 7.61 and 85.18 ± 6.87%), the heart rate at VT (168.5 ± 13.79 and 157.23 ± 16.15 bpm), as well as for the %FCMAX at which VT occurred in these athletes (89.23 ± 6.98 and 90.05 ± 1.04%). In conclusion, cyclists and triathletes showed different aerobic capacity because they had unlike physiological adaptations.